sac spider

sac spider, (family Clubionidae), widespread family of nearly 700 species of nocturnal spiders. that build silken tubes, or sacs, under stones, in leaves, or in grass. Sac spiders range in body length from 3 to 15 mm (about 0.12 to 0.6 inch) and have eight eyes in two rows. The taxonomy of the group is contentious. Chiracanthium inclusum, found throughout the United States, is venomous to humans and is often found indoors. Its greenish white to cream-colored body is about 8 mm (0.3 inch) long. It is sometimes placed in the family Cheiracanthiidae, the yellow sac spiders.